When undertaking an engine build of this level, there is always some sort of hurdle. Add into the equation the use of newly developed parts and you'll definitely find surprises. In this installment, we initially planned on featuring the balance and assembly of the block, but we ran into some problems of our own. However, it would be an injustice to you, as the reader, to make every job seem like a cakewalk (like certain TV shows that start with Horsepower). Due to the tight schedule of our build, we wanted to give you the reality of our problems and what we did to get through them. Blueprinting and building engines isn't an easy undertaking and should never be taken lightly. In this installment we are going to go over the importance of pre-fitting components and balancing the rotational mass of the engine assembly.
Progress is the most important part of any build/project. Even with these roadblocks, we were still able to do what we needed to move forward. This goes back to what we've been stressing from the beginning: be meticulous. From here, we'll be sending out any component with a friction surface to WPC for treating and assembling the motor. Be on the lookout for the next installment of our 750hp KA24DE(T).
The pin journals are moved...
The pin journals are moved in closer together for the box-style design. This closed up the gap to where a stock rod's small end no longer fit.
The small end of the rod is...
The small end of the rod is sent out to the machine shop to get milled down. We take a bit extra off for clearance between the piston and rod.
The rods and crank we received were from preproduction units. The big end of the rod journal was on the tight side, while the crank OD was on the big side. When we went to measure out for the bearings, we found that the clearance was to the point that there was no bearing to select from. This was an easy fix, however, since we were at the end of the spectrum where the rod ID could be opened up to a bearing spec of our choice. We also found that the small end of the rod was too thick for our box-style piston. Since the wrist pin was shrunken down, the actual thickness of the rod wouldn't fit. The thickness of the rod measured out to 24.79mm while the gap from pin journal to pin journal was 20.3mm. Since our piston is already so narrow, we decided that it would be wiser to have Ultra Performance Machine mill down the small end than cut out anymore material from the piston. We had them cut the rod down to 19.3mm giving us a 0.5mm clearance on each side of the rod.
Here you can see on the white...
Here you can see on the white marks where the block interferes with the crank. This can be easily grinded down to allow the proper amount of clearance.
Another problem we ran into was the crank itself. Since the factory crank is only half counterweighted, the factory casts the block with this in mind. Unfortunately for us, our new fully countered crank hits against small sections of the block and griddle.
With the block cut away we...
With the block cut away we also deburr any casting flash to promote oil flow and ensure no debris comes off the block and enters the lubrication system.
Here the girdle is also clearanced...
Here the girdle is also clearanced for the now fully countered crankshaft.
The bright side is that the area interfering with the crank has no real critical usage and can easily be grinded. Since we were already grinding away at the bottom of the block, we decided to clean up any casting imperfections that were leftover. As we discussed in the previous article, this will allow oil to flow freely back into the pan.
Our digital scale reads down...
Our digital scale reads down to the 1/10th of a gram. To ensure that the scale is calibrated correctly, we use a certified stainless steel precision weight.
Once the parts were back, we were finally able to balance the pistons and rods. Here we are looking out for vibration caused by rotational imbalance. Since the engine is moving in a rotational motion, it experiences vibration much like a wheel. This vibration especially at 7,000 to 8,000 rpm can contribute to premature ring, piston skirt, and bearing wear. When revving up an engine with a base rpm of 6,000 to 8,000 rpm, the amount of centripetal force on the crank increases exponentially. This is a direct correlation with the amount of vibration experienced by the engine.
When taking measurements of...
When taking measurements of the block, the torque plate should be installed.
From where we left off, we just received the block back from Ultra Performance Machine. We wanted to double-check that the final bore matched our specifications. To do this, we have to bolt the torque plate back on to simulate the distortion seen from a cylinder head. From here, we went on to work on the pistons and rods. This is where some of our problems started.